


Jack to the Future

by gothyringwald



Category: Supernatural
Genre: Attempt at Humor, Castiel is Jack Kline's Parent, Dean Winchester in Denial, Dean Winchester is Jack Kline's Parent, Established Relationship, Inspired by Art, M/M, POV Dean Winchester, Pining, Pre-Slash, Season/Series 05, Time Travel, and also some non-specific future time
Language: English
Status: Completed
Published: 2021-03-18
Updated: 2021-03-18
Packaged: 2021-03-26 02:20:00
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,883
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/30098787
Author URL: https://archiveofourown.org/users/gothyringwald/pseuds/gothyringwald
Summary: When Jack accidentally travels back in time, meeting younger versions of Dean and Cas, Dean learns some things about their future selves that just can’t be true…can they?
Relationships: Castiel & Jack Kline & Dean Winchester, Castiel/Dean Winchester
Comments: 84
Kudos: 753





	Jack to the Future

**Author's Note:**

  * For [archervale](https://archiveofourown.org/users/archervale/gifts).
  * Inspired by [Jack goes back to the past by accident and finds his dads, it doesn’t go well](https://archiveofourown.org/external_works/778044) by archervale. 



> Inspired by [this suuuuuper cute and lovely art](https://archervale.tumblr.com/post/645596057371328512/this-is-so-dumb-lol-jack-goes-back-to-the-past-by) by archervale
> 
> Set somewhere in the middle of season five I think? Mostly because there were some references I wanted to make XD Oh, also, because of that, Cas is kinda antagonistic to Jack when he first arrives - if you want more details in case you think it might upset you, you can head to the end notes! The fic is, overall, meant to be funny though
> 
> And vague references to John Winchester’s A+ parenting

Dean is cleaning his gun, all the parts laid out on the desk of their latest fleabag motel, when there is a shift in the air. He knows without looking that someone else— _something_ else—is in the room with him. And his gun is in pieces. Great.

He closes his fist around the grip, just to have something in his hand, slowly standing and turning on the spot. There’s a kid standing between the two beds, hand raised in an awkward wave, a small smile on his face. He looks harmless, but that doesn’t count for much.

‘Who are you?’ Dean does a quick scan of the room, making sure the kid didn’t bring friends. ‘What are you?’

The kid’s face falls a little and his hand drops to his side. ‘It’s me.’

‘OK, “me”, got a name?’

‘I’m Jack. Don’t…’ Jack’s eyes widen and he opens and closes his hands. ‘You don’t know me.’

‘Uh, no.’ There’s something about the kid, though. He reminds Dean of… ‘Cas!’

Cas has materialised, standing between Dean and the kid, angling himself like a shield. For a moment, Jack’s face lights up, but it soon falls again. Probably something to do with the murderous look Cas is fixing on him.

‘Good timing,’ Dean says.

‘I was keeping an eye on the motel after you told me where you were and I sensed something.’ Cas doesn’t take his eyes off of Jack, and there’s steel in his voice. ‘And now I see why.’

‘Cas, it’s me, it’s Jack.’ The kid steps forward, the motion awkward and halting.

‘Do _not_ move,’ Cas says, ‘and do not address me like we know each other.’

‘We do.’ Something flickers over the kid’s face, like something’s occurring to him. ‘Or we will…’ he mutters. ‘I went too far.’

‘You gonna tell me what’s got your feathers so ruffled?’ Dean asks Cas. ‘He some kinda mega demon, or something?’

‘That’—Cas points at Jack—‘is an abomination.’ And if the kid had looked upset before, he looks _gutted_ , now.

Dean almost feels bad for him, even if it makes no sense for him to be put out by what Cas said. What monster cares about being called an abomination?

‘I think something went wrong,’ Jack says.

‘Yes. Something went wrong when you came here to harm this man. Who sent you?’

‘I wouldn’t hurt Dean. And I sent myself.’

Cas advances on Jack but Dean catches him by the shoulder. ‘Let me go, Dean.’

‘Hey, look, before you go getting all smitey, wanna tell me what kind of abomination we’re talking here?’

‘It’s a Nephilim.’

It rings a bell. Dean’s read about them, during one of his many apocalypse study sessions, but he’s not sure enough of what it is to know what kind of threat it poses. ‘That’s an angel thing, right?’

‘Yes,’ Cas says, ‘the offspring of a human and an angel. They are…monsters.’

‘So, angel’s _aren’t_ junkless.’

‘ _Dean_.’

‘I’m not a monster.’ Jack doesn’t sound entirely certain, even as he takes another half-step forward. He tries a smile. ‘I’m your son. From the future.’

For the first time since he got here, Cas’s fury wavers. ‘No—’

Something suspiciously close to, but definitely not, jealousy fizzes in Dean’s blood, churns in his gut. So, Cas knocks up some human chick in the future. Guy isn’t going to stay a virgin forever, is he? That’s if the kid is telling the truth. ‘Well,’ Dean says, licking his lips, ‘Cas, you old dog.’ His voice sounds wrong.

‘No, I—’ Cas flicks a look at Dean. His eyes are wide and Dean remembers when he took Cas to that “den of iniquity”. ‘I would know if this _thing_ were mine.’

Jack flinches. He has every time Cas calls him ‘thing’ or ‘abomination’. It pings something for Dean but he lets it slide for now, and says, ‘Got some kinda angelic paternity test we can do?’ He holds his hands up at Cas’s glare. ‘Just in case.’

‘We don’t even know if he truly is from the future.’

‘Yeah, that had occurred to me.’ Dean rolls his eyes, then looks at the kid. He looks like a regular kid. _And a lot like Cas_ , an unhelpful voice supplies. Dean ignores it. This dweeby, totally sweet, normal-looking kid is a half-angel-half-human baby monster. ‘OK, kid,’ Dean says, ‘if you’re from the future, tell us something that hasn’t happened, yet.’

Jack opens his mouth, but Cas says, ‘Dean, if it hasn’t happened, how are we to know if it’s true? He could make it up. We haven’t experienced the future, yet.’

‘I—’ Dean throws his hands up. ‘Well, I don’t know!’

‘I could tell you something only someone close to you would know?’ Jack says.

‘OK, shoot.’

‘Dean, it could be a trick—’

‘Just let the kid talk.’

Cas huffs and Jack looks thoughtful for long moments until he says, ‘A long time ago, you and some other angels went to kill a Nephilim.’ He looks uneasy, and there’s tension in the air. ‘You didn’t realise until a really long time after that it wasn’t the right thing to do.’ He frowns. ‘But…you don’t know that, yet.’

It’s not what Dean was expecting. He was thinking something along the lines of a favourite movie, not this. He looks at Cas, and Cas looks like the world is collapsing around him.

Shit. This kid really is Cas’s. And if he’s Cas’s he must be good, right? And he still has this _look_ , like when he keeps flinching, and Dean gets, it now. He knows that look. He saw it in the mirror often enough when his own old man—

But Jack doesn’t carry that weary resignation Dean had, eventually, looks _shocked_ , so this is new. Not that Dean is surprised, if he’s Cas’s kid, Dean knows Cas would treat him right.

Cas shakes his head. ‘You’re lying. You must be.’

‘Cas, c’mon, man, just…ease off on the kid.’ Dean swallows thickly. ‘I think he’s telling the truth.’

‘No, Dean, he can’t be. It wasn’t wrong.’ Cas looks stricken, and Dean doesn’t know if it’s at the revelation of what he tells Jack in the future, about that other Nephilim, or that Jack must really be his son. Cas gathers himself and says, ‘I would never have relations with a human!’

And that shouldn’t sting like it does, hearing Cas say that. Not that Dean has any interest in who Cas does, or doesn’t, want to have “relations” with. And who even says relations? God, Cas is such a dork. Dorky and weird and weirdly adorable. Weirdly dorky. _Dorky_. Dean clears his throat and crosses his arms. ‘Well, apparently you _do_.’ He nods at Jack.

Jack is looking between them with a frown, and then his eyes widen. ‘Oh. You mustn’t be together, yet.’

He obviously means Cas and whoever his mom is, but, still, Dean says, ‘Who?’

‘You two.’

There’s a ringing sound somewhere. At first, Dean thinks it’s a phone, then he realises it’s in his ears. He opens and closes his mouth. ‘What?’

‘You’re my dads,’ Jack says, simply. Like he hasn’t just dropped the biggest damn bombshell. Screw the apocalypse, this kid says he and Cas are _together_. Like…together? There’s _no_ way—

‘That’s not possible,’ Cas says, brow furrowed.

‘Hey! You’d lucky to have me. I’m a damn catch, OK?’ Dean blinks. ‘I mean, not that _I_ would…’ Shit. Abort. Abort!

Cas rolls his eyes. ‘Dean, I meant—’

‘Wait!’ Dean thrusts out a hand. Jack’s words have finally sunk in. He said Cas and Dean are his dads. Both of them. Jack is a half-angel-half-human teen monster. They’re _both_ his dads. He’s half angel, half…

Oh crap. Dean has no idea how angel sex even _works_. Did future-Dean knock up an angel? A dude angel? Could he even… Oh, god. What if it was it the other way—

The room is spinning and Dean’s throat is tight and his head is hot and his legs are buckling and—

Strong arms slide under his own, keeping him on his feet. Not that he was about to _faint_ or anything. He’s not some swooning maiden in a bodice ripper. Not that he knows anything about those, either.

‘Dean.’ Cas’s hands are on his shoulders, now, and he’s peering into Dean’s eyes. ‘Are you OK?’

‘Am I OK?’ Dean resists the urge to lean into Cas’s touch and, instead, bats his hands away. ‘Are you kidding me?’

‘No.’

‘Cas, some kid pops into my motel room, tells us he’s our half-angel-half-human baby from the future, like that’s not ten kinds of bizarre, even for us, so, no, I’m not OK.’ The room isn’t spinning so much, now, but he’s still hot and he’s not so sure that burger he ate for lunch wants to stay in his stomach.

‘It’s obviously not true, Dean.’

‘Well, it _is_ ,’ Jack says, ‘but—’

‘What?’ Dean talks over Jack, still focussed on Cas. ‘Am I not good enough to be your baby daddy?’

Cas blinks at Dean like he’s grown an extra head. ‘I don’t know what that means.’

‘It means—’

The door slams open and Sam stomps in with his big Sasquatch feet, blissfully unaware of the chaos inside. ‘Hey, Cas,’ he says, dropping his satchel. Then, his gaze swings slowly to Jack and he’s on alert. ‘Who’s our new friend?’

‘I’m Jack.’ Jack has his hand raised in that little wave again. ‘I’m from the future.’

‘OK… Cool?’ Sam gives Cas and Dean a careful look, raising his brows. ‘Not cool?’

‘No idea,’ Dean says, ‘but he’s our son, apparently.’

‘Whose?’

‘Ours.’ Dean waves a hand between him and Cas.

The noise Sam makes, then—somewhere between a whimper and a choked cough—would, under other circumstances, either fill Dean with concern or glee. But, right now, he’s still stuck on his future self having a _Nephilim baby_ with his guardian angel and current crush. Not crush. Dean does _not_ have a crush on anyone, and certainly not on any angel in a rumpled trench coat.

‘He is not our son, Dean. I told you, it’s not possible.’

‘I don’t know,’ Sam says, the colour returning to his face. ‘He does look like Cas. Like, a lot.’ He adds, ‘And he has your eyes, Dean,’ in that irritating mock-innocent tone Dean knows too well.

Without thinking, Dean says, ‘He doesn’t, he has Cas’s—’ He clamps his jaw.

Sam is smirking, the asshole.

Dean points his finger at Sam. ‘Shut your mouth.’

‘Sam’—Cas turns to Sam, fixing him with a long-suffering look—‘it is not possible that Dean and I would have a child together.’ A troubled look crosses his face. ‘Unless I took another vessel…’

‘You don’t,’ Jack says, ‘but—’

‘Yeah, seems I’m not good enough for Cas,’ Deans says, because he hasn’t made _enough_ of an idiot of himself.

Sam’s eyebrows shoot into his hairline and Cas turns back to Dean. ‘Dean,’ he says, ‘we could _not_ have a child together because neither of us has a uterus.’

In the distance, a trucker leans on their horn. Sam makes that noise again. Dean coughs. Jack blinks. ‘Right,’ Dean says.

Cas squints at him. ‘I had assumed you knew how reproduction works.’

If Dean thought his face was on fire before, it’s nothing compared to now. ‘Pshh. I know how it works! I just…’ He looks at Sam, but he’s no help because he has that constipated look like he’s trying not to laugh, and Dean ends up saying, ‘Angels?’ with a shrug.

Cas is still squinting at him and Sam looks two seconds away from imploding. Luckily, Jack pipes up again, saying, ‘Oh, I understand.’ He smiles. ‘Neither of you is my _biological_ father.’

‘Well, then who is?’ Dean says.

‘Lucifer.’

That expression about being so quiet you could hear a pin drop? Dean’s pretty sure it’s true as he and Cas both fix equally questioning looks on Sam.

‘Hey.’ Sam holds up his hands. ‘Don’t look at me.’ He blanches. ‘I think.’

‘Oh, no, Lucifer was possessing the president when he impregnated my mother.’

‘ _What_?’

There’s another stunned silence and then everyone starts talking at once:

‘If he’s Lucifer’s son, he must be destroyed,’ Cas says. ‘A regular Nephilim would be powerful enough but Lucifer’s son would have powers untold.’

‘If he’s from the future, won’t he just be born again, anyway?’ Sam says.

‘Maybe he could help us with our apocalypse problem,’ Dean says. ‘Lucifer’s kid’s gotta have some intel, right?’

‘I just want to go home,’ Jack says. Quietly at first, so that it barely registers to Dean. But when Dean and Cas and Sam keep talking, he says it again, ‘I want to go _home_ ,’ eyes flaring gold and all the furniture in the room rattles and the walls shake.

Dean’s first instinct is to attack the thing that just created a mini-earthquake in their motel room. But the kid looks _scared_. And he looks like Cas. And something in Dean is screaming to help him, not hurt him. It’s confusing, and it makes no damn sense, but when Cas reaches out, Dean stops him.

‘Dean, let go of me,’ Cas says, as though he couldn’t shake Dean off. ‘You saw what he did.’

‘He’s scared.’ Dean adds, softer, ‘You’re— We’re his dads, or in the future we are, and he’s _scared_.’

Cas stares at Dean, his gaze searching and penetrating, and then he drops his hand. His brow furrows. ‘Oh.’ He looks at Jack, and something crosses his face, like he’s really looking at him properly for the first time. ‘I’m…sorry,’ he says.

‘It’s OK.’ Jack sighs. ‘I am, too. I didn’t mean to do that to the room! And I know you thought I wanted to hurt you, but I wouldn’t. And I didn’t mean to travel back in time in the first place.’ His shoulders sag. ‘I mess everything up.’

‘Welcome to the family,’ Dean says. Jack beams. It does something funny to Dean’s chest, the same feeling he used to get when Sammy would look up at him like he was the best thing ever. Shit. This kid is his kid. ‘So, if we’re not your bio dads, we adopt you, or something?’ He doesn’t look at Cas, but he can feel his gaze on him. Because they may not have had a baby, but they’re apparently _together_ in the future.

‘Yes,’ Jack says. ‘But, um…’

‘What?’ Sam coaxes.

‘Well, I’ve seen a lot of time travel movies, and I just realised that I probably shouldn’t tell you anything. What if I mess up the future?’

Dean can’t help it, he barks out a laugh and claps Jack on the shoulder. ‘I like you, kid.’

‘Jack,’ Sam says, ‘how did you _get_ here? Do you have powers like angels?’

Jack explains that he does, in some ways, but he hadn’t actually meant to travel back in time. Or, not so far. He’d been trying to go back a few minutes, because he’d broken one of Dean’s favourite mixing bowl—which, what the heck, Dean has a favourite mixing bowl?—and felt bad. That he overshot by a good few years troubles Dean and he can tell it troubles Cas, too. If he can do something like this by accident…

The thing is, Dean really likes the kid. He’s goofy and awkward, and Dean’s gut tells him he’s a good kid. Even Cas seems to have softened toward him. And if Dean had a hand in raising Jack, then his future self must be all right. They clearly come out of this apocalypse mess on the other side, anyway.

They spend a good ten minutes arguing the merits of grilling Jack about how they get out of it, but it turns out he’s only been told the vaguest details about it all. And, as much as he might be able to help them, Cas says it’s too much of a risk.

But they also decide that they can’t let Jack try to get back to the future—Dean’s _Where he’s going he don’t need roads_ is met with an eye-roll from Sam, a blank look from Cas and Jack saying ‘I love that movie!’—on his own, or who knows where he’ll end up, or what else he might do?

‘I can’t send him back, but I can help Jack concentrate his powers,’ Cas says, ‘make sure he gets back to where he belongs.’

He raises his hand to Jack’s forehead but then Sam says, ‘Wait!’ and Cas drops his arm to his side. ‘What?’

‘I think Jack might have been right about the future, about messing it up.’ Sam looks at Jack. ‘Do we ever talk about meeting you before, in the future?’ He screws his face up. ‘Uh, you know what I mean.’

Jack frowns. ‘No.’

‘That could just mean we don’t _tell_ him,’ Dean says.

‘Yeah, but… I don’t know, I just have a feeling, Dean,’ Sam says. ‘I think he should erase our memories. Can you do that, Jack?’

‘I—’ Jack looks from Sam to Cas to Dean. ‘I think so.’

‘That’s encouraging,’ Dean mutters. At Sam’s pissy look, he says, ‘Fine, yeah, OK, let’s do this thing.’ Great, he’s signing up to get his memory wiped by his future adoptive son. His fucking life.

Jack’s hands twitch at his sides and he steps forward, his hands raised.

‘Hey, before you scramble our noggins, I gotta know one thing,’ Dean says. When Jack nods, he adds, ‘If you’re Lucifer’s kid, how come you look so much like Cas?’

Cas gives him a questioning look, which Dean pretends not to notice.

‘Really, Dean?’ Sam says. ‘That’s the one thing you want to know?’

‘What?’ Dean shrugs. ‘I’m not gonna remember, so why ask anything important?’ And this isn’t important, Dean’s just curious. That’s all.

‘Um, well,’ Jack says, ‘I guess I wanted to?’ When Dean only raises his brows, Jack adds, ‘Cas looked after my mother when she was pregnant. So, I knew him, before I was born, and— And he was good and kind and I wanted to be like him.’

‘Oh.’ Dean lets out a low, long breath. ‘That explains that, then.’ He looks at Cas, who looks…awed. And a little proud. Dean’s lips twitch.

‘I…’ Cas swallows thickly. ‘Thank you.’ He looks quickly at Sam, then for longer at Dean, before looking back to Jack. If Dean didn’t know better, he’d think Cas’s eyes were glittering. ‘I’m sorry again, for…’

‘It’s…OK,’ Jack says. He steps toward Cas, then stops, seeming to think better of whatever he was going to do. ‘I should go now.’

Cas nods.

‘It was good to meet you, Jack,’ Sam says.

‘Yeah, looking forward to meeting you again,’ Dean says. ‘Or, uh, for the first time.’ He hates time travel.

Jack gives a brief, tight smile. He looks at Cas and says, ‘I’m ready.’

Cas raises his hand again and lays his palm on Jack’s forehead; Jack raises his own hands, stretching them toward Sam and Dean and Cas. Cas’s eyes flare ice-blue and Jack’s flare gold.

There’s a shift in the air and a cracking sound and Dean blinks. He looks at Sam and Cas and says, ‘Hey, when did you guys get here?’

—

Dean is cleaning his gun, all the parts laid out on the table in the library, when there is a shift in the air. He knows without looking that someone else is in the room with him. ‘Hey, kiddo,’ he says, laying the magazine down. ‘I was just about to make lunch when I’ve finished this. I know you don’t need to eat, but what do you feel like?’

‘Dean.’ Jack’s voice cracks, sounds a little desperate.

Something’s wrong. Dean turns, whip-fast, pushing himself to his feet. He only gets a glimpse at Jack—all sad eyebrows and glassy eyes—before Jack flings himself at him. Arms so tight around Dean’s neck he can barely breathe.

‘Uh…’ Dean pats Jack’s back. ‘Everything OK?’

‘I’m just glad to be here.’

Dean huffs. He loves the kid, to the moon and back, but, damn, he’s weird sometimes. Just like his dad. His _other_ dad. ‘Well, I’m glad you’re here, too.’

There’s movement over Jack’s shoulder; Cas has walked in, hands sunk into the pockets of his—Dean’s—jeans, one shoulder of his ridiculous grandpa cardigan slipping down. He pauses when he sees Jack and Dean.

‘Is everything OK?’ Cas’s brow is furrowed in concern.

‘Jack’s just glad to be here,’ Dean says, giving Cas a “no idea what’s going on” look.

‘Cas!’ Jack pulls away from Dean, turning to Cas, and giving him the same treatment he gave Dean moments earlier.

Cas smiles that small smile Dean knows is reserved for Jack related happiness, and squeezes Jack tight.

‘I’m sorry,’ Jack murmurs.

Cas tenses and pulls back to look at Jack. His eyes narrow. ‘What for?’

‘Um.’ Jack raises his brows and smiles nervously. He lifts his shoulders. ’Nothing really.’

Dean puts a hand on Jack’s shoulder. ‘Jack.’ ‘I didn’t mean to do it.’

‘Do what?’

There are a few moments of silence, where Dean thinks of all the things Jack could have done, and trying to figure out how they can fix it, before Jack says, ‘Time travel.’

‘You time travelled?’ Cas says.

‘Just a little bit.’ Jack smiles. ‘And I’m back now. And I didn’t do anything bad.’

‘I—’ Cas looks at Dean, silently asking what they should do.

Dean shrugs. What _can_ they do?

‘I won’t do it again,’ Jack says. ‘Unless…it’s OK? There are some historical events I wouldn’t mind seeing.’

Dean and Cas give him matching “I don’t think so” looks.

‘But I’ll just read about them,’ Jack says.

‘Good idea,’ Cas says. He considers Jack, head tilted. ’Is that all that happened?’

‘Well, I met your younger selves, but I erased your memories so I wouldn’t mess up the future.’

Dean groans. He looks at Cas, who looks the same way Dean feels, and opens his mouth, then closes it. ‘You know what, let’s…deal with this after lunch.’ He pinches the bridge of his nose. ‘I can’t think about time travel on an empty stomach.’

As they walk out of the library—Jack a few steps ahead, Dean and Cas behind, their hands brushing between them—Dean mutters, ‘Time travel.’ He shakes his head and looks at Cas. ‘He gets that from you, you know.’

Cas rolls his eyes, but he slides his hand into Dean’s as he says, ‘Of course, Dean.’

‘Wait, Dean, I forgot something,’ Jack says as they step into the kitchen.

‘What, don’t tell me you un-sunk the Titanic or something?’

‘No, I…’ Jack bounces on his toes, eyebrows pinched together. ‘I broke your mixing bowl. That’s why I went back in time. I thought I could go back to before I broke it but I went too far.’

Dean blinks and then he laughs. And then he can’t stop. He laughs until his sides ache and Cas is giving him a long-suffering look—lips twitching beneath it—and Jack just looks anxious.

‘Don’t sweat it, kiddo,’ Dean says, ruffling Jack’s hair, ‘I can get a new one.’

**Author's Note:**

> Re top notes: Cas refers to Jack as an abomination, it and thing multiple times, and also approaches him in a threatening way (he assumes Jack is there to hurt Dean) which Dean notes is upsetting for Jack before Cas ends up apologising when he realises he was wrong
> 
> Anyway, thanks for reading! :D I've never written anything inspired by someone's art - or anything - before so I'm nervous but this was SO much fun to write XD
> 
> Please feel free to come find me on tumblr [@ersatzangel](http://ersatzangel.tumblr.com/) for SPN stuff or [@gothyringwald](http://gothyringwald.tumblr.com/) (which is my main and vaguely multi-fandom) - you can also find [a rebloggable thing for this fic over there if you wish](https://ersatzangel.tumblr.com/post/645949740371099648/jack-to-the-future) :) and remember to [check out the art](https://archervale.tumblr.com/post/645596057371328512/this-is-so-dumb-lol-jack-goes-back-to-the-past-by) if you haven’t :D
> 
> ETA: just wanna say I do consider Sam Jack's dad, as well, and know Jack sees him that way, but I was getting myself confused writing this as it was lol XD


End file.
